The present invention relates to improvements in or relating to cation exchange membranes for use in electrochemical cells and, in particular, to strongly cationic selective membranes which combine a low electrolytic resistivity with a high permselectivity, and to a method for the production thereof.
Cation exchange membranes have been proposed for use in various electrochemical applications, including chlor-alkali cells, fuel cells and energy storage/power delivery devices. In these devices, the cation exchange membrane serves to separate the compartments of the cells, whilst providing a conducting pathway for cations through the cell. For certain applications, such as for use in the chlor-alkali process or fuel cell applications, the membranes may also have metallic catalytic electrodes formed on the surface thereof. Proposals for the preparation of such membrane/electrode composites include the process as disclosed in U.S. Pat. No. 4,959,132 whereby a metallic catalytic film is formed on the surface of the membrane by the reduction of a water soluble metallic salt impregnated into the membrane to form the metal.
For use in electrochemical applications, a cation exchange membrane requires a high voltage efficiency, i.e. a low resistance. Low resistance membranes generally have a high water content and are not very selective, i.e. have a low current efficiency. What is required is a membrane with both low resistance and high selectivity.